Designing a gripper for a robotic arm to pick and place various objects using an aperture-type mechanism.

1. Jack Gillies & Jeremiah Gill
For AUTOTECH 2AC3
Instructor: Lucian Balan
SOLIDWORKS DESIGN
AND SIMULATION
PROJECT
March 19th, 2015

2. Constraints:
-Must be able to grip 3 prismatic shapes:
-Must be controlled by given servo motor, 5 rotations to close/open
-Must fit onto standard robot tool interface
-All parts must be able to be manufactured
-Assembly without interference
-Must use standard fasteners
-Robust and self-contained

3. Final Design

4. Final Design

5. Redesign
- After we finished the modeling, we realized the gripper isn’t
big enough to fit the cube
- We measured the cube face to face and ignored the
hypotenuse length of the cube
- Redesign took about 10 hours – Would have been easier if
we modeled more parametrically.

6. Final Design
-522.19 grams
-137 parts, 32 Unique parts
-Can grip objects up to 80mm in
width
- 84.3 mm maximum height from
arm interface
- 194 mm maximum width (to back
of servo)

7. Final Design

8. Assembly Animation

10. Inspiration
-Camera Shutter closes equally around central point
-Will make contact without lateral slip with any part.
-Operates by turning overlapping “leaves” towards inside
-Leaves are turned by pins which are driven by a central
turning ring

11. Initial Design
-5 Leaves overlapping (2mm thick)
-Leaves Spaced by washers of same thickness
-Assembly held in by retaining ring

13. Initial Design
-5 Pins of varying length (increments of 2mm) to turn the
leaves
-Pins are pushed through slots in turning ring
-Portion of bevel gear drives turning ring

14. Issues
-Overlap of leaves may cause “tipping” or
rocking of gripped piece
-We decided to mirror whole assembly so 2
apertures grip piece at different heights

15. Retaining Case
-Revolved profile of all turning parts to
create casing to retain rotational motion
-Mounting features for Motor assembly
-Identical mounting brackets for M6 bolts
-Upper holes machined for M4 screws to
hold in upper leaf base.
-This part will probably have to be casted
in aluminum.

16. Drive Train
-Total ratio needed is 39/1800 (turning ring degrees
per motor degree)
-Simple bevel gear and pinion would not be suitable
-Additional gears achieve following ratio:
15 𝑃1
41 𝐺1
15 𝑃2
41 𝐺2
18 𝐵𝑃1
120 𝐵𝑃2
≈ 39/1800
-Gearbox created to mount gears from motor to
Retaining case

17. Drive Train

18. Turner Synchronization
-Lower turning plate is driven by bevel gear
-Upper turning plate is connected by turner
synchros (shown in pink)
-Assembly is held together with set screws
-Plates slide inside grooves of retaining case

19. Spacer Cuff
-This part spaces the whole assembly out
from the arm interface
-This allows the gripper to grip taller parts in
closer to the center

20. Design Drawbacks
-Weight
-May shear objects
-Large width – cannot fit into small spaces
-Can only grip objects up to 80mm in diameter
-Many parts only serviceable if completely
disassembled
-Leave assemblies are 54 mm apart – parts shorter
than this will only be gripped by one leaf assembly.

21. Questions?